Biotransformation of Cardenolides from Calotropis procera and Their Cytotoxic Potential against Human Mammary Gland Carcinoma Cells

Background: Poekilocerus pictus (Fabricius 1771), a painted grasshopper, sequesters cardenolides from its food plant, the Apple of Sodom or Aak, Calotropis procera (Aiton) W.T. Aiton (Family-Asclepiadaceae). In our present investigation, we were able to isolate Pseudomonas aeruginosa KRK6 from the intestine of Poekilocerus pictus responsible for the biotransformation of cardenolides. Methods: Pseudomonas aeruginosa KRK6 was grown in methanolic extracts of Calotropis procera and the modified cardenolides were detected by Liquid Chromatography-Mass Spectrometry (LCMS) and also used to induce apoptosis in cancer cells (MCF-7 cells and T-47 D). Result: The modified cardenolides CPMEP6 was found to induce apoptosis in human breast adenocarcinoma cells (MCF cells-IC50 =6.31±0.4 µg/mL, T-47D cells-IC50 = 10.1±1.02 µg/mL). Phosphatidylserine exposure and DNA fragmentation suggested apoptosis in treated cancer cells. CPMEP6 induced apoptosis in cancer cells via the mitochondrial pathway by down-regulating BCL-2 protein expression and up-regulating BAX protein expression.